Unix

• Unix Shell Primer
• Grep and Regex
• GPG Primer

Git

• Introductory Workshop to Git
• Git Primer
• Briefing on Git
• Introduction to GitFlow
• Specifying Revisions
• Patches: Apply, Format and Apply from Mailbox
• Rewriting History
• Briefing on Git's Internals
• Pro Git book

PHP

• PHP 5.6 (far from perfect but it's a gentle and brief introduction)
• Programming PHP (for a slow introduction)
• The new stuff of PHP 7
• Data Structures in PHP
• PHP guidelines
• PHP PSR guidelines
• PHP DocBlock guidelines
• PHP Cookbook (for advanced topics in PHP)
• Really helpful REGEX web tool
• ICU Message Format web tool

Protocols

• Briefing on HTTP
• HTTP Status codes for semantic REST APIs
• Twitter API v1 Documentation

ActivityPub

• ActivityPub Seminar Resources by Diogo
• ActivityPub Official Website
• ActivityPub SocialHub

OAuth2

• Aaron Parecki's guide
• BShaffer's lib has a good doc
• Introduction by Digital Ocean

Information Management

• A First Course in Database Systems
• Briefing on XML
• JSON Tutorial
• Modern SQL
• XML
• PostgreSQL
• Database System Implementation

Software Engineering

• Software Engineering (part 1)
• Software Engineering (part 2)
• Wikipedia on DevOps
• Wikipedia on Code Coverage
• Wikipedia on ORM
• Wikipedia on MVC
• Wikipedia on Quality Assurance
• Wikipedia on Quality Control
• Dev Cycles
• Testing and Code Reviews
• APIs, Modelling, etc.
• Briefing on Design Patterns
• Briefing on SOLID
• Simple Systems Have Less Downtime

Cybersecurity

• Huge TL;DR on WebSecurity
• OWASP's Web Testing Guide
• EBook on Cybersecurity

Web Frontend

UI

• Briefing on CSS3
• Briefing on HTML5
• Display Fonts
• Carbon Design System
• Apple Design Guidelines
• Material Design Guidelines
• Adobe Colour Palette Web Tool

UX

• Directing User Attention via Visual Flow on Web Designs
• How Screen Colour Affects Time Perception

Accessibility

• W3C (Strategies, standards, resources to make the Web accessible to people with disabilities)
  • Get Resources for Content Writers
  • Tips for Getting Started Designing for Web Accessibility
  • Web Accessibility Tutorials for Developers
• IndieWeb Tags
• Microformats Wiki
• A11Y
• Contrast Checker based on W3C: AERT and WCAG
• Any Browser
• Why simple UIs are often preferable
• Bootstrap Satire